Correlation of Crude Oil Steam Distillation Yields With Basic Crude Oil Properties

Steam distillation can occur in reservoirs during steam injection and in-situ combustion processes. To estimate the amount of vaporized oil caused by steam distillation, we established correlations of steam distillation yields with the basic crude oil properties. These correlations were based on steam distillation tests performed on 16 crude oils from various pans of the U.S. The gravity of oils varied from 12 to 40 deg. API [0.99 to 0.83 g/cm3]. The viscosity of oil ranged from 5 to 4,085 cSt [5 to 4085 mm /s] at 100 deg. F [38 deg. C]. The steam distillations were performed at a saturated steam pressure of 220 psia [1.5 MPa]. One oil sample was used in experiments to investigate the effect of steam pressure (220 to 500 psia [1.5 to 3.4 MPa]) on the steam distillation yield. The experiments were carried out to a steam distillation factor (Vw/Voi) of 20, with the factor defined as the cumulative volume of condensed steam used in distillation, Vw, divided by the initial volume of oil, Voi. At a steam distillation factor of 20, the distillation yields ranged from 13 to 57% of the initial oil volume. Several basic crude oil properties can be used to predict steam distillation yields reasonably well. A correlation using oil viscosity in centistokes at 100 deg. F [38 deg. C] can be used to predict the steam distillation yield within a standard error of 4.3 %. The API gravity can be used to estimate wields within 5.6%. A gas chromatographic analysis was made for each crude oil to obtain the component boiling points (simulated distillation temperatures). A correlation parameter was selected from the simulated distillation results that can be used to estimate the steam distillation yields within 4.5%. Introduction Steamflooding has been used commercially to recover heavy oils for several decades. Although it is considered a heavy-oil recovery process, it has been demonstrated to be an effective and commercially feasible process for recovering light oils. To enhance the effectiveness of the oil recovery process, it is important to fully understand and utilize the basic steamflooding mechanisms. Willman et al. investigated the mechanisms of steamflooding. They concluded that oil viscosity reduction, oil volume expansion, and steam distillation are the major mechanisms for oil recovery. Since then, more research has been done on all phases of steam injection. However, steam distillation and its ramifications on recovery have not been quantified fully because of lack of experimental data. Steam distillation can lower the boiling point of a water/oil mixture below the boiling point of the individual components. SPEJ P. 937^